Electrically releasable hook and loop fastener

ABSTRACT

An electrically releasable form of hook and loop fastener ( 10 ) allows one half of the fastener to release from the other half without applying direct physical force to either half. The hook elements ( 21 ) of the fastener are formed of a shape-memory alloy material ( 27 ) such as commercially available Ninitol. Release of the hook half ( 14 ) of the fastener from the loop half ( 12 ) is accomplished by passing an electrical current through the shape-memory alloy material to straighten the hooks ( 21 ) so that they release their engagement with the loops ( 18 ). The flow of electricity through the hook half energizes the Ninitol material ( 27 ) to change its shape, either expanding or contracting in length; the change in shape is made to act against another length of material ( 28 ) that remains fixed in length or changes shape in an opposite direction so as to cause the hook shape to straighten toward a rod shape. Upon termination of the flow of electrical energy, the hooks return ( 21 ) to their hook shape, ready for re-engagement with the loops ( 18 ) upon conventional mating of the two halves of the fastener. Release and re-engagement can be repeated, substantially indefinitely.

This invention relates generally to hook and loop fasteners of the typethat are well known and commercially available under the TrademarkVELCRO. More specifically, the invention relates to hook and loopfasteners in which the two halves of such a fastener can be releasedfrom engagement with each other via external means without theapplication of direct, external physical force.

Hook and loop fasteners have been well known in the fastener art formany years and they have been used successfully in many and widelydiverse applications. The secure engagement of one half to the other andthe substantial force required to separate the two halves appear to havecontributed significantly to the popularity of this type of fastener.However, the force that must be applied to achieve separation of the twohalves, the brief but finite time required to achieve separation, andthe incremental or progressive nature of the separation process, havebeen found to make the separation process difficult and/orunsatisfactory in some instances.

The inherently incremental nature of the known separation process,requiring the two halves to be progressively “peeled” apart, can makethe use of hook and loop fasteners unsatisfactory and/or extremelydifficult in applications that lack sufficient clearance for a peelingor tilting motion. Similarly, the finite time required to “peel” onehalf from the other sometimes precludes the use of hook and loopfastenings when relatively “instant” separation, such as the separationof snap fasteners, is required. Hook and loop fasteners designed for“heavy duty” applications with substantial holding force can requiresimilarly substantial separation forces. Separation forces under thesecircumstances may exceed the physical ability of certain users, therebyfurther limiting the application of these worthwhile fastening devices.

SUMMARY OF THE INVENTION

The present invention is directed to providing a hook and loop fastenerin which the time and force required to separate the two mating halvesare reduced to a minimum. This invention is further directed toproviding hook and loop fasteners that can be fabricated readily usingavailable materials and known techniques. Another advantage of the hookand loop fastener of this invention is that disengagement of the twohalves can be automated if desired. Further, disengagement can even beaccomplished remotely, without direct application of external physicalforce.

Hook and loop fasteners in accordance with this invention can befabricated in generally conventional manner, but, commercially available“shape-memory” alloy material such as Nitinol must be used to form atleast part of the hook elements. Shape-memory alloy material comprises akey element of the hook and loop fastener of this invention.

An important aspect of shape-memory alloy material, also known as“muscle wire,” is that it is electrically responsive so as to change itsshape when an electrical current flows through it. More specifically,shape-memory alloy material in wire form can be made to contract inlength in response to the flow of electricity through the wire. Thisinvention relies on this property of shape-memory alloy wire to allowthe two halves of the hook and loop fastener to disengage from eachother by passing electrical energy through the hook portion of thefastener. That is, the hooks are caused to straighten so as to loosetheir “hook” shape when an electrical potential is applied.

By selectively applying electrical energy to cause the hooks to assume astraight-line “memory” shape, the characteristic interlocking engagementof the hooks with the loops is released, and the two halves of thefastener are, in effect, instantly disengaged from each other. In lightof this disclosure, it can now be seen that the application ofelectrical energy to a suitably constructed hook and loop fastener canbe made to cause disengagement of the loop portion of such a fastenerfrom the hook portion without the application of external physicalforce. That is, if desired, disengagement of the fastener assembly canbe effected from a remote location using electrical energy only. In thisregard, it will be understood that physical displacement generally willbe required to achieve actual separation of the two halves of afastener. In many applications such displacement can be achieved throughthe force of gravity alone, after the hook elements are “straightened.”However, in view of this disclosure, it will be apparent to those havingordinary skill in this art that various different arrangements can beemployed utilizing the disengagement method and apparatus of thisinvention to achieve physical separation of two fastener halves.

In the disclosed embodiment of the invention, a two-part hook and loopfastener assembly of conventional configuration is formed usingelectrically conductive flexible material for part of the hook elements.More specifically, in the hook element half of the fastener, the hookelements are formed at least in part, of electrically conductiveshape-memory alloy material such as Nitinol. It is known that Nitinol inwire or narrow strip shape, can be made to contract in length inresponse to the flow of electrical current. This invention contemplatesthe use of this kind of shape-memory alloy wire or strip. Althoughexpansion or contraction of the material is possible, contraction isbelieved to be the more commonly available and therefore preferablecharacteristic.

It will be understood readily by those having ordinary skill in thisart, that wires or strips made of materials having an expansion orcontraction characteristic can be joined in parallel relationship withanother “inert” material to form a single element, similar to thebimetallic element of a conventional thermostat. Such an element can bemade to distort in a desired manner when one of the two materialscontracts or expands. The hook elements of the fastener of thisinvention are constructed accordingly. That is, the hook-shaped elementsare formed of a length of shape-memory material joined in parallelrelationship with an inert material, the combination being formed tohave the desired hook shape. Accordingly, a normally hook-shaped elementhaving the contracting shape-memory material positioned along the outercurved circumference of the hook shape will tend to straighten into astraight-line or “rod” shape when the flow of electricity through theshape-memory “muscle wire” causes the outer circumference of the hook toshorten from its un-energized length. Shortening the outer circumferenceof the hook has the effect of “opening” the hook shape by straighteningit toward a “rod” shape as the inner and outer circumferences of thehook approach equality in length. Thus, the usual, or non-memory form ofthe hooks corresponds to the conventional “hook” shape used in hook andloop fasteners, whereas the energized, “memory” shape of the normallyhook-shaped elements is that of a substantially straight line or rod,free of any significant hook shape.

It can be seen readily that the substantially straightened rods on thefirst half of the fastener, free of any reversely bent “hook” shape,will disengage from and be free of locking or fastening engagement withthe loop elements of the second half of the fastener. The formed,hook-shape elements are transformed into their straight rod “memory”condition by the flow of electricity through the shape-memory alloy wirematerial in accordance with the known characteristics of such materials.

In accordance with this invention, the base surface material of the hookhalf-portion of the fastener preferably will be electrically conductive.Hooks cut and formed of lengths of stock made of two materials joined inthe manner herein identified can be produced and anchored in generallyupright orientation to a desired base surface using suitable, knownfabrication techniques. Techniques for achieving the necessaryelectrical connection between the shape-memory alloy portion of eachhook and the electrically conductive base surface material can be chosensimilarly. The choice of techniques used for this purpose will bedecided, in most instances, based upon economic considerations.

Economic considerations are expected to affect in like manner, thechoice of techniques used to facilitate the flow of electricity throughthe shape-memory alloy material. For example, with the hook portion ofthe fastener fabricated in accordance with the preceding observations,the loop half of the fastener may be formed of suitable electricallyconductive material so that electricity can be made to flow through thehook elements in an electrical path extending from the hook half of thefastener to the conductive material of the loop half-portion.

As an alternative to establishing an electrical path from the hooks tothe loops, each hook element may be formed of two separate,electrically-conductive lengths of material that are electricallycoupled to each other at the open end of the hook; in this manner, theelectrical path through each hook element extends through one of thelengths of material from its base end to its free end and through theother length of material from its free end to its base end. Separateelectrical connections to the base end of each of the two lengths ofmaterial can be established by various means such as, for example,forming the base surface of the hook portion from a composite sheetmaterial having a first conductive layer and a separate conductive layerseparated by an electrically insulating layer, with one of theconductive elements of a hook coupled to the first conductive layer andthe other conductive element of the hook coupled to the secondconductive layer.

In brief, means are provided for making electrical connections to thetwo ends of the electrical path, however constituted, so thatultimately, an electrical potential difference is imposed between theends of the shape-memory alloy portion of each hook. When an electricalpotential difference is imposed, the current flowing through theshape-memory alloy material of the hook elements will cause them toassume their shortened, or extended, “memory” condition, therebystraightening and disengaging the hook elements from the loop elementsso as to release the two halves of the fastener from each other.Generally, the straightened condition of the hook elements will bemaintained by the flow of electricity. If an electrical path isestablished between the two halves of the fastener, it is apparent thatcurrent flow will be interrupted as soon as the two halves haveseparated. Alternatively, if the electrical path is established withinthe hooks independently of the loops, then current flow will continueuntil it is deliberately interrupted as by a switch or the like. Withinthe field of shape memory material technology, choosing materials havinga longer or shorter “recovery time” will determine how long the hookswill remain in substantially straightened condition following theinterruption of electrical current flow.

It can now be seen that release of the two fastener halves fromengagement with each other can be accomplished without application ofany external physical force whatsoever, and accordingly, release can becontrolled remotely and, if desired, automatically. All that is requiredis the application of electrical energy to cause current flow throughthe muscle wire portion of each hook element in the hook portion of thehook and loop fastener assembly. Preferably, a switch or other suitablemeans of controlling current flow is connected in series with theelectrical path that includes the hook portion of the assembly, so thatcurrent flow through the path can be enabled or interrupted, selectivelyand substantially at will.

These and other features, and advantages of this invention will be mademore apparent to those having skill in this art, by reference to thefollowing specification considered in conjunction with the accompanyingdrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified, partial side elevation view of the two halves ofa hook and loop fastener assembly in accordance with this invention;

FIG. 2 is a partial side elevation view of the hook and loop fastenerhalves of the assembly of FIG. 1, shown in engaged relationship;

FIG. 3 is a partial side elevation view of the hook and loop fastenerassembly of FIG. 1, showing the appearance of the fastener in responseto the flow of electricity therethrough;

FIG. 4 is a simplified side view of the hook and loop fastener of thisinvention showing details of a corresponding electrical circuit; and

FIG. 5 is a simplified side view of another embodiment of the hook andloop fastener of this invention showing a modified electrical circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following description, certain specific details of the disclosedembodiment such as circuits, interconnections, materials and techniques,etc, are set forth for purposes of explanation rather than limitation,so as to provide a clear and thorough understanding of the presentinvention. However, it should be understood readily by those skilled inthis art, that the present invention may be practiced in other forms andembodiments which do not conform exactly to the details set forthherein, without departing significantly from the spirit and scope ofthis disclosure. Further, in this context, and for the purposes ofbrevity and clarity, detailed descriptions of well-known apparatus,circuits and methodology have been omitted so as to avoid unnecessarydetail and possible confusion.

Referring now to the drawings, the hook and loop fastener assembly 10 ofFIG. 1 may be seen to comprise a loop half-portion 12 and a mating, hookhalf-portion 14. Loop half-portion 12 in this case incorporates loopbase surface 16 having a plurality of loop elements 18 extendingsubstantially normally therefrom. The mating hook half-portion 14 ofassembly 10 incorporates a hook base surface 20 having a plurality ofhook elements 21 extending substantially normally therefrom.

The shape and overall function of loop elements 18 are typical of theconventional structure of the loop half-portions and loop elements ofknown hook and loop fasteners; accordingly, these aspects of thisstructure will not be described in detail herein. In this regard, itshould be noted that each loop element 18 is characterized by an opencenter portion 26 defined by the surrounding “loop” shape. And, itshould be understood further that loop elements 18 may be formed andattached to loop base 16 in various, well known manners, such as a massof interconnected helical loops of fibrous material fastened to the base16, as shown in the drawings or, individual loop shapes may formedintegrally with the material of loop base 16 by known fabricating and/ormolding processes.

In turn, each hook element 21 of hook portion 14 extends from a fixedend 22 to a free end 23 at the open end 25 of hook shape 24, remote fromfixed end 22. Fixed end 22 is attached to and extends from hook basesurface 20. In the conventional manner of hook and loop fasteners,hook-shapes 24 extend into and between loop elements 18 when hookportion 14 is urged into opposed, substantially abutting relationshipwith loop portion 12. When the two fastener half-portions 12, 14 areurged toward each other, at least some of the hook shapes 24 at the freeends 23 of hooks 21 pass through and become entangled in the openportions 26 of loops 18 as shown in FIG. 1, thereby “locking” the twohalves 12, 14 of fastener assembly 10 together, in a well-known manner.

In accordance with established prior art practice, separation ofhalf-portions 12, 14 can be achieved by applying sufficient physicalforce in opposite directions to pull the two parts away from each other.Separation in this manner “unbends” the resiliently flexible hook shapes24 until they straighten enough to slip out of the open centers 26 ofloops 18. This is the conventional and well-known method of operation ofhook and loop fasteners. With proper selection of known and availablematerials, the hook and loop fastener of this invention will separate inaccordance with the prior art as well as in accordance with theinvention herein disclosed.

In accordance with this invention, loop portion 12 may formed ofelectrically conductive material so that an electrical current path canbe established incorporating hooks 21 and loop half portion 12. That is,loop half portion 12 having base surface 16 with a plurality of loopelements 18 extending in substantially normal relationship therefrom,may be formed as a unitary structure of electrically conductivematerial. Alternatively, if desired, loop half portion 12 can be made ofa non-conductive material that has been coated with a conductivematerial, provided that problems involving abrasion and eventual wearingaway of the conductive coating are overcome satisfactorily. And as willbe disclosed herein, loop portion 12 may remain entirely non conductivein accordance with another embodiment of the invention. A consistentrequirement for each form of loop portion 12 is a reasonable flexibilityof the loops 18 as well as base surface 16 so that engagement anddisengagement of the mated halves 12, 14 of the fastener assembly 10 canbe accomplished as intended.

The structure and function of hook portion 12 defines the significantaspects of this invention, in that hook elements 21 are constructed soas to straighten in response to the flow of electrical current throughthe hook. In accordance with this invention, at least part of each hookelement 21 is formed of shape-memory alloy material such as Nitinol,which is frequently identified as “muscle wire”. It is a knowncharacteristic of shape-memory material that it may be made so as toexpand or contract in response to electrical energy. In wire form,shape-memory material accordingly may either shorten or elongate inresponse to the application of an electrical potential. In thisinvention, generally flexible and electrically conductive shape-memorywire is incorporated into hook elements 21 in the hook shape shown inFIGS. 1 and 2. Hook elements are configured, as explained in thefollowing, so that when an electrical potential is applied between thefree end 23 and the fixed end 22 of element 21, the element willsubstantially straighten from the hook shape 24, shown in FIGS. 1 and 2,to the generally straight-rod shape extending between fixed ends 22 andfree ends 23 of hook elements 21, as shown in FIGS. 3 and 4.

Hook elements 21 of this invention utilize the expansion/contractioncharacteristics of shape-memory wire to alter the shape of the elementsfrom the usual hook shape to a substantially straight rod shape inresponse to the flow of electrical energy. This is accomplished in amanner akin to the operation of a thermal bimetallic element respondingto heat energy.

As shown most clearly in FIG. 2, the composite body of each hook element21 comprises a first length of flexible shape-memory wire or stripmaterial 27, coupled in side-by-side parallel relationship with a secondlength of preferably different flexible material 28. In repose, that isin the absence of electrical energy, the composite body maintains its“hook” shape. Upon application of an electrical potential differencebetween the fixed end 22 and the free end 23 of shape-memory length 27,expansion or contraction of length 27 acts against the relativelyfixed-length curvature of material length 28 to cause the curvature tostraighten into or near straight-rod shape. The straightening need onlybe enough to permit hooks 24 to loose their “grip”, that is theirengagement within the open centers 26 of loops 18.

Specifically if “muscle wire” of the type that contracts in response toelectrical energy is being used for element 27, hook elements 21 will beconfigured so that shape memory material length 27 is positionedproximate the outer curved edge of hook shape 24; then, the length ofmaterial 27, representing the outer circumference of the curved hookshape 24, will grow shorter in response to the flow of electricity,while the dimension of inner length 28 will remain unchanged.Accordingly, hook shape 24 will straighten as the dimensions of itsinner and outer circumferences approach equality.

With reference to expansion and/or contraction of the shape memorymaterial, it should now be recognized that shape-memory wire or stripthat elongates in response to electrical energy, can be adopted for usein place of, or in combination with, material that contracts, by usingthe shape-memory material for the inner curvature portion of hook shape24 instead of, or in combination with, the outer curvature portion. Acombined use of expansion-type material for the inner curvature of thehook shape, with contraction-type material for the outer curvature ofthe hook shape, may be particularly effective when added force isrequired for heavy duty applications or when particularly stiff flexiblematerials are employed.

As suggested previously herein, and as illustrated in FIG. 4 of thedrawings, electrical connector means 30, 32 are associated with hookfastener half-portion 14 for imposing an electrical potential differencefrom an electrical power source 34 between the fixed end 22 and the freeend 23 of shape memory material length 27 of hook elements 21. That is,the source of electricity 34 is connected in series with an electricalon-off control switch 40, and both source 34 and switch 40 in turn areconnected in series, via electrical connector means 32,33, with theelectrical path that includes the length of shape memory material 27,such that the electrical paths represented by hook elements 21 liesbetween switch 40 and source 34.

With reference to the electrical coupling of connector means 32, 33, tohook elements 21, it should be understood that the “ends” of theelectrically conductive material does not necessarily requireconnections at the actual physical extremities of the material andconnections proximate the ends thereof generally will be acceptable forthe purposes herein disclosed. The electrical connector means 32,33 maybe of any suitable and known form of electrical connector, includingboth separable connectors and terminal connectors. If separableconnectors are used it will be understood that only one half of each oftwo connectors need be coupled to the fastener of this invention, whilethe remaining half of each separable connector is reserved forestablishing electrical connections with external devices, sourcesand/or equipment.

To provide for electrical coupling to hooks 21 when length 28 comprisesconductive material connected in series with length 28 at the free endsthereof, base 20 of hook portion 14 may comprise a composite having afirst conductive sheet or layer 29 separated and electrically insulatedfrom a second conductive sheet 30 by an intermediate insulating sheet orlayer 31. With hook elements 21 mounted to this form of base 20,apertures 35 formed in top sheet 29 allow extensions of conductivematerial length 28 to extend through sheet 29 without electrical contactso that they can extend into electrical contact with second conductivesheet 30. Conductive shape memory length 27 of each hook element 21similarly contacts sheet 29 directly. Accordingly, electrical connectormeans 32 coupled to sheet 29 and electrical connector means 33 coupledto sheet 30, readily allow an electrical potential difference to beimposed between the fixed ends 22 of conductive lengths 27, 28 of hookelements 21.

In this embodiment of the invention, as shown in FIG. 4, a source ofelectricity 34 is connected in series with an electrical on-off controlswitch 40 and both source 34 and switch 40 in turn are connected viaelectrical connector means 32,33, in series with the path defined bylengths 27, 28 of hook elements (21) and conductive sheets 29, 30.

In the alternative embodiment of the invention illustrated in FIG. 5,hook elements 21 incorporate only a single length of conductive material27, as previously described herein, and loop elements 18 are formed ofelectrically interconnected continuous coils of conductive material suchas wire that, accordingly, provides an exposed conductive surface forthe conductive surface of the hook elements to engage. In thisembodiment of the invention, base 20 of hook portion 14 incorporates atleast a single sheet of conductive material 29 electrically connected toshape material lengths 27 of hooks 21, with electrical connector means32 electrically connected to sheet 29 so that one side of an electricalsource 34 may be connected to lengths 27 of hooks 21. Further, basesurface 16 of loop portion 12 may either incorporate a separate singlesheet of conductive material 30 electrically coupled to loop elements 18and to connector means 33, or, conductive sheet 30 may be avoidedentirely and electrical connector means 33 may be connected directly toconductive loops 18, to complete the electrical connection to the secondside of electrical source 34.

As in the operation of the embodiment of the invention illustrated inFIG. 4, in the embodiment of FIG. 5 as well, a source of electricity 34is connected in series with an electrical on-off control switch 40 andboth source 34 and switch 40 in turn are connected in series, in thiscase, with the path defined by hook elements (21) and loop elements (18)via electrical connector means 32,33.

Although a preferred embodiment of the method and apparatus of thisinvention has been illustrated and described, those having skill in thisart will recognize that various other forms and embodiments now may beenvisioned readily without departing significantly from the spirit andscope of the invention disclosed herein and set forth in theaccompanying claims.

1. An electrically releasable hook and loop fastener assembly (10)comprising: a loop fastener half-portion (12) having a loop fastenerbase (16) with a plurality of loop elements (18) extending therefrom; ahook fastener half-portion (14) having a hook fastener base (20) with aplurality of hook elements (21) extending therefrom; said hook elementshaving a fixed end (22) mounted to said hook fastener base and a freeend (23), remote from said fixed end, defining a hook shape (24); saidhook elements being dimensioned to mechanically engage said loopelements when said loop fastener half-portion and said hook fastenerhalf portion are pressed into contact with each other; said hookelements comprising a first length of flexible material (28) and asecond length of flexible, electrically responsive and electricallyconductive shape-memory material (27) of the type that changes from afirst configuration to a second configuration in response to electricalcurrent flow therethrough; means (32, 33) associated with at least saidhook fastener half portion for applying an electrical potentialdifference between said fixed end and said free end of said hookelements; and, said length of shape-memory material being positioned tosubstantially straighten said hook shape in response to change in shapeof said shape memory material upon application of an electricalpotential difference between the ends thereof.
 2. The electricallyreleasable hook and loop fastener assembly (10) of claim 1, furthercomprising: electrical connector means (32,33) electrically coupled toat least said hook fastener half portion of said fastener assembly toform an electrical series circuit with said hook element between them.3. The electrically releasable hook and loop fastener assembly (10) ofclaim 1 or 2, wherein said first and second lengths of material arecoupled together in parallel abutting relationship.
 4. The electricallyreleasable hook and loop fastener assembly (10) of claim 3, wherein saidsecond length of material (28) is electrically conductive and saidsecond length of material is electrically insulated from said firstlength of material (27) along the lengths thereof, said first and secondlengths of material being electrically coupled to each other to form aseries circuit, proximate the said free end of said hook element (21).5. The electrically releasable hook and loop fastener assembly (10) ofclaim 1, wherein said first length of material (27) is shape memorymaterial of the type that contracts in response to the flow ofelectricity; and said second length of material (28) is shape memorymaterial of the type that elongates in response to the flow ofelectricity; said assembly further comprising electrically conductivematerial associated with said hook surface base, said electricallyconductive material being electrically connected to said fixed end ofsaid shape-memory material of each of said hook elements; and, a firstelectrical connection site coupled to said electrically conductivematerial on said hook surface base and a second electrical connectionsite coupled to said electrically conductive surface of said loopelements, for causing an electrical current flow through saidshape-memory material between said fixed and said free end of each ofsaid hook elements when said hook elements are in electrical andphysical contact with said loop elements.
 6. An electrically releasablehook and loop fastener assembly (10) in accordance with claim 4, furthercomprising: first electrical connector means (32) electrically coupledto said fixed end of said first length of material, and secondelectrical connector means (33) electrically coupled to said fixed endof said second length of material (28).
 7. An electrically releasablehook and loop fastener assembly (10) in accordance with claim 5, furthercomprising: first electrical connector means (32) electrically coupledto said fixed end of said first length of material, and secondelectrical connector means (33) electrically coupled to said fixed endof said second length of material (28).
 8. The electrically releasablehook and loop fastener assembly (10) of claim 1, wherein said loopelements have an electrically conductive surface thereon forelectrically contacting said first length of material of said hookelements when said first and second half-portions of said connectorassembly are urged into engagement with each other.
 9. The electricallyreleasable hook and loop fastener assembly (10) of claim 1, wherein saidloop elements comprise continuous electrically interconnected coiledwires for electrically engaging said conductive first length ofmaterial, when said first and second half-portions of said connectorassembly are urged into engagement with each other.
 10. An electricallyreleasable hook and loop fastener assembly (10) in accordance with claim7, further comprising: first electrical connector means (32)electrically coupled to said fixed end of said first length of material,and second electrical connector means (33) electrically coupled to saidloop elements.
 11. An electrically releasable hook and loop fastenerassembly (10) in accordance with claim 8, further comprising: firstelectrical connector means (32) electrically coupled to said fixed endof said first length of material, and second electrical connector means(33) electrically coupled to said loop elements.
 12. A system forelectrically releasing hook and loop fastener halves from engagementwith each other, said system comprising: a loop fastener half-portion(12) having a loop fastener base (16) with a plurality of loop elements(18) extending therefrom; a hook fastener half-portion (14) having ahook fastener base (20) with a plurality of hook elements (21) extendingtherefrom; said hook elements having a fixed end (22) mounted to saidhook fastener base and a free end (23), remote from said fixed end,defining a hook shape (24); said hook elements being dimensioned tomechanically engage said loop elements when said loop fastenerhalf-portion and said hook fastener half portion are pressed intocontact with each other; said hook elements comprising a first length offlexible material (28) and a second length of flexible, electricallyresponsive and electrically conductive shape-memory material (27) of thetype that changes from a first configuration to a second configurationin response to electrical current flow therethrough; said length ofshape-memory material being positioned to substantially straighten saidhook shape in response to change in shape of said shape memory materialupon application of an electrical potential difference between the endsthereof; electrical on-off control switch means and a source ofelectrical energy connected in series with each other and with saidfirst length of shape memory material to form an electrical path throughsaid first length of material when said switch is on and to interruptsaid electrical path when said switch is off; and, means (32, 33)associated with at least said hook fastener half portion for applying anelectrical potential difference between said fixed end and said free endof said hook elements.